Mott criticality and pseudogap in Bose-Fermi mixtures

TL;DR

This paper investigates the Mott transition in a mixed Bose-Fermi ultracold atom system, revealing a pseudogap at criticality and potential pairing or weakly first-order transition mechanisms.

Contribution

It introduces a detailed analysis of the Mott transition in Bose-Fermi mixtures, highlighting the pseudogap behavior and the role of critical mode interactions in transition dynamics.

Findings

Fermi surface coexists with Bose-Einstein condensate at weak interactions

Spectral function exhibits pseudogap behavior at criticality

Interaction between critical modes can induce p-wave pairing or weakly first-order transition

Abstract

We study the Mott transition of a mixed Bose-Fermi system of ultracold atoms in an optical lattice, where the number of (spinless) fermions and bosons adds up to one atom per lattice, n_F+n_B=1. For weak interactions, a Fermi surface coexists with a Bose-Einstein condensate while for strong interaction the system is incompressible but still characterized by a Fermi surface of composite fermions. At the critical point, the spectral function of the fermions, A(k,w), exhibits a pseudo-gapped behavior, rising as |w| at the Fermi momentum, while in the Mott phase it is fully gapped. Taking into account the interaction between the critical modes leads at very low temperatures either to p-wave pairing or the transition is driven weakly first order. The same mechanism should also be important in antiferromagnetic metals with a small Fermi surface.